Collet for machine tools



Dec. 17, 1940. A. MUSSARI COLLET FOR MACHINE TOOLS Filed March 14, 1939 2 Sheets-Sheet l Dec. 17, 1940. A. MUSSARI COLLET FOR MACHINE TOOLS 2 Sheets-Sheet 2 Filed March 14, 1939 3t I I llllllll m n v INVENTOR. Humour NUJJAB/ W j/w dm a W ATTORNEYS Patented Dec. 1' 7, 1940 I v UNITED STATES PATENT OFFICE COLLET FOR MACHINE TOOLS Anthony Mussari, Erie, Pa., assignor to The Warner & Swasey Company, Cleveland, Ohio, a. corporation of Ohio 'Application March 14, 1939, Serial No. 261,715

2 Claims. (Cl. 279-51) This invention relates to collets and particus e a ge it i necessary that the collet D larly to collets which are used in certain types of be removed and replaced with another set of machines, such as screw machines and lathes, pads which are thicker or thinner, depending wherein bar stock of various sizes and shapes is upon whether the stock is changed from a. smaller 5 fed through a hollow spindle. to a larger size, or which have their inner faces 5 In machinesof the general type mentioned S ab y co ed the new Shape Of Stock above, there is located in the hollow spindle a If e Shape Of the Stock is Variedso-called collet which is adapted to grip the bar The changin o the p for the P p se stock and hold it stationary while the portion mentioned above is time-consuming since it is of the stock which projects beyond the spindle necessary to e Ve e guard from the head- 10 isbeing operated on by the tool or tools, and stock and then remove the hood from the spin later to release the stock so as to permit it to die so as to expose the forward end of the colbe fed forwardly-for the next operation or cycle let. Usually the p are s ur d to t inner of operations to be performed by the tool or tools. feces o the forward ends of the let law y Such a collet is usually formed from a tubular screws, and these Dad uring screws must be 15 member slotted to provide flexible spring jaws to removed one at a time. After new pads have the inner faces of which are secured pads which been secured to thecollet jaws it is necessary to are adapted to engage the stock. replace the hood on the spindle and then re- The outer faces of the collet jaws are tapered, Place the guard Oh the headstockand there is provided on the forward end of the The principal O j 0f the Present invention 20 spindle a so-called hood having a conicalopenis to fac itate the pplication or removal of the ing through which the stock is adapted to procollet pads and to so secure the pads to the collet ject. The conical or tapered face of this open- .l WS t at the p y be removed and y ing is adapted to engage tapered faces of the readily replaced with others without the necesjaws and to cam them inwardly to bring the sity of removing the guard and hood or disturb- 25 pads into gripping relation with the stock, th ing the collet and without the necessity of macollet being designed to be moved axially of the n pulating screws 0 eq va means to fasten spindle so as to bring the tapered faces of the the pads to the collet jaws orto remove them. jaws into or out of camming relation with the A further object is to provide a collet which tapered face of the hood. It is moved in one embodies to a high degree the features of ef- 30 direction to cause the collet pads to engage the ficiency and economy in the respects that the stock and in the opposite directionso that the pads can be quickly removed or applied, and jaws may spring outwardly and release the stock. when applied are effectively held in place with In some machines the collet is moved forwardly the result that the collet functions as an efficient when the pads are to grip the work, in which element in gripping and holding the work and 35 case the collet is termed a push-out collet, while in releasing it to permit the bar stock to be fed in other machines the collet is moved rearward-' forwardly through the spindle. ly for this purpose and in such machines the Briefly stated, the invention comprises the collet is known as a pull-back collet. use of snap fasteners of the flexing spring finger I 40 The hood referred to is at the front of the type instead of screws to secure the pads to the 40' headstock and is mountedon an enlarged forcollet jaws, these snap fasteners being operable wardly projecting portion of the spindle with to secure or release the pads from the front end the camming surface which is adapted to 00- or nose of the collet lying within the hood, thus operate with the tapered forward ends of the colavoiding the necessity of disturbing or changing let jaws carefully centralized with respect to the the positions of the collet hood and guard when 45 axis of the spindle. Generally, as a safety facthe snap fasteners are actuated in changing tor or safety element, the hood is surrounded by pads.

a cover which is fastened to the front end of the A single snap fastener is preferably utilized to headstock in which the hollow spindle is joursecure a pad to the jaw and to release it therenaled. from, this snap fastener being preferably radial- 50 7 As stated above, bar stock of various sizes and ly disposed substantially centrally with respect shapes is designed to be operated upon and fed to the sides and the ends of the pad. through the hollow spindle. For each size or The invention may be further briefly sumshape of stock a given set of collet pads is emmarlzed as consisting in certain novel details ployed. Each time the size or shape of the stock of construction and combinations and arrange- 55 ments of parts which will be described .in the specification and set forth in the appended claims. I v

In the accompanying sheets of drawings,

Fig. 1 isa fragmentaryvertical sectional view through a portion of a machine tool equipped with my improved collet, part of the machine tool being broken away, the machine tool here shown being such as to employ a collet of the push-out type;

Fig. 2 is a longitudinal sectional view of the collet removed from the machine tool, the section being taken substantially along the line 2-2 of Fig. 3;

Fig. 3 is an end view of the collet shown in Fig. 2 looking toward the left of Fig. 2;

Fig. 4 is a view similar to Fig. 1 with the machine tool utilizing a collet of the pull-back type;

Fig. 5 is a view similar to Fig. 2 showing the pull-back collet of Fig. 4;

Fig. 6 is an end view similar to Fig. 3 showing the collet of Fig. 5;

Fig. 7 is a detached end view of the pad utilized in the collet of the preceding views;

Figs. 8 and 9 are respectively a sideview and an end view of thesnap fastener utilized in the collets. of the preceding views;

Fig. 10 is a view similar to Fig. 2 showing, however, only the forward portion of the collet and illustrating a modified form of snap fastener for detachably securing the pad to the collet jaw;

Fig. 11 is a view similar to Fig. '7 showing the pad formed to accommodate the snap fastener of Fig. 10; and

Figs. 12 and 13 are views similar to Figs; 8 and 9 respectively showing the modified form of snap fastener illustrated in Fig. 10.

headstock is a hood I! having a conical opening with a tapered inner face is for camming the jaws of the collet inwardlyto work engaging position. Surrounding the hood is a guard 20 which is adapted to be secured in the usual mannor to the front face of the headstock. Inside .of the spindle I1 is' a collet shifting sleeve 2! which rotates with the spindle but is freely movable in-an endwise direction therein. The forwardend of the sleeve 2| is in abutting relation with the rear end of the collet which is shown at 22, this collet being of the push-out type. The work is. in this instance, in the form of round bar stock designated 8 extending through the spindle II, sleeve II and collet 22. When the sleeve is moved forwardly it pushes the collet forwardly so that the outer tapered faces of the collet jaws (to be referred to presently) engage and are cammed inwardly by the tapered inner face ll of the hood, and when the endwise pressure on the sleeve II is relieved, the effect of the spring tension imposed in the Jaws and on the amazing tapered faces of the hood and laws is such as to move the collet rearwardly and at the same time move the sleeve 2| in the same direc- 1|. The usual way of moving the sleeve forwardlytion is illustrated in Fig. 1 which shows the rear end of the spindle surrounded by a cone 23, the cone being engaged by fingers 24 of a shifter including a holder 25 which is screwed onto the extreme rear end of the spindle H. The inner ends of the fingers are provided with abutments 26 which when the outer ends of the fingers are cammed outwardly by thecone engage a shouldered portion at the rear end of the sleeve 2| and move it forwardly and when the cone is withdrawn from the outer ends of the fingers, the pressure'of the tapered surfaces of the collet jaws on the tapered face of the hood moves the collet inwardly and restores the sleeve to its previous position. The cone is adapted to be shifted by a lever. 21 which may be manually or otherwise operated. The lever is shown as. mounted on a bracket 28 mountedqon aportion of the gear box containing the feed gears which do not concern the present invention and need not be described in detail.

'the headstock is designated I and the hollow work spindle ila, the same being journaled in the headstock as before by anti-friction bearings Ida, only the forward bearing being here shown. Secured to the forward end of the spindle as before is a hood I8a which in this instance has an inner tapered face Isa .tapered in the reverse direction from that illustrated in Fig. 1.

' hood is surrounded by a guard Ila secured to the headstock as before. g In the hollow spindle is a collet shifting sleeve Ila the forward end of this sleeve beingin this The instance screwed into the threaded rear end of the collet which is designated :20. To cause the collet pads to grip the bar stock S the collet is pulled back by rearward movementimparted to onto the rear end of the sleeve are beyond the rear end of the spindle, and this holder carries fingers 24a the outer ends of which are adapted to be spread apart by a cone 23a mounted as before on the spindle and shiftable by a lever 21a. In this instance the rear ends of the'iingers a are counterweighted as shown at b so that the forward ends of the fingers will normally tend to move inwardly by centrifugal force. In this construction the abutments Ila. of the fingers 24a engage a ring 261) which abuts against the rear end of the spindle. Accordingly, when the cone 23a is movedto the left or to the position shown in Fig. 4, so as to spread the fingers a, the abutments its press against the ring lib which in turn press against the spindle "a, and the effect of this is to move the holder for the fingers and therefore the sleeve lid and the, collet 21a rearwardly, thusmoving the collet jaws inwardly to work engaging position. When the cone is moved to the right to become free of the fingers 24a, the en'ect of the spring or tension in the collet jaws .and' the engagement of their outer tapered faces withthe tapered surface of thehood Ila is to move the collet and sleeve forwardly and thus release thev bar stock.

Referring now to the construction of the collet illustrated in Figs. 2, 8, 7, 8 and 9, the collet 22 comprises a body portion in the form of a tubular member 2l-with an enlarged forward end 280 and slotted from its forward end rearwardly 'the sleeve Ila. In this instance the holder for the sleeve shifter here designated 15a is screwed to near its rear end forming fingers or jaws 30. The collet body is usually formed from heattreated steel so that the jaws 30 have considerable resilience or spring in order that they can 5 be pressed-inwardly by the hood to work gripping position and when released will again spring outwardly to normal position and thus release the work so that it can be-fed through the spindle. It is to be noted that the outer faces of the jaws are tapered as shown at 3| to conform to the tapered surface I9 of the hood for the purpose previously explained.

In this instance the forward end of the collet body 29 is counterbored to form a clearance for the collet pads 32 each of which is in the form of an. arc-shaped member generally made of hardened steel. In this instance the collet has three spring jaws and therefore accommodates three of the collet pads 32 and, as herein illustrated, the inner surfaces of the pads are arcs of circles to accommodate round bar stock S. However, it is to be understood that the number of jaws and therefore the number of pads provided on the collet may be varied as desired, and if stock other than round stock is fed through the spindle, the

inner faces of the pads will be shaped accordinglyso that the collet will in all instances be capable of effectively gripping the stock regardless of its contour and size. It will be understood that pads of different thicknesses are required for stock of different sizes, a thicker pad being required for stock of small size, and vice versa.

Suitable means is provided on the engaging surfaces of the pads and colletjaws to prevent endwise movement of the pads on the jaws and to center them or cause them to seat squarely thereon. This is accomplished in this instance by providing substantially midway between the inner and outer ends of the pads a tongue and groove interfitting connection between the pads and the inner surfaces of the jaws. In this instance the pads are provided on their outer faces with areshaped square-cut ribs 33 which fit closeiyinto correspondingly shaped grooves on the inner faces of the jaws. However, the arrangement of the ribs and grooves may be reversed, i. e., the grooves may be cut on the outer faces of the pads and the inner faces of the jaws may be provided with the ribs to fit the grooves of the pads.

59 Additionally, in this instance the inner ends of the pads bear against a shoulder formed by the counterbore, but I do not regard the use of abutting faces at this point as essential as the tongue and groove interfitting'. parts adequately serve the purposes mentioned, but the shoulder formed by the counterbore may be used to advantage in aligning or centering the pads when they are being placed in the jaws of the collet.

To detachably secure the pads to the collet in a manner such that they can be either placed in position or removed without disturbing the collet, the hood, and the guard, in other words, to accomplish the objects of the invention stated'in 'the early part of the specification, I secure the pads in place by the use of snap fasteners, one

may be carried by the jaws and the pads may be provided with suitably-formed openings so that the heads of the fasteners may snap into suitably shaped openings in the pads.

In the construction illustrated in Figs. 1 to 9, 5

the snap fasteners are in the form of tubular .rounded shouldersv at the free ends of the finger 340.

Each collet jaw is provided with an opening 35,

. and at the base of the opening a beveled shoulder 20 35a is provided so formed that when the pad'is inserted in the collet and pressed outwardly, the slotted protruding end of the fastener is pressed up in the narrow part of the opening35 and as the rounded resilient head 34d passes the shoulder 35a the fingers spring outwardly or expand so that the pad is effectively held in position but can be readily detached from the jaw by prying the pad away from the jaw, as by inserting a suitable tool between their engaging surfaces. This can 30 ,be done from the front of the machine without disturbing the collet, the hood, or the guard, as previously noted.

It should be noted that in the construction illustrated in Figs. 1 to 9 the opening of the pad 35 which receives the threaded end of the snap fastener extends through the arc-shaped rib 33 and the opening provided in the jaw to receive the protruding spring end of the fastener extends through the base of the groove which receives 40 the rib.

With the fpull-back collet illustrated in Figs. 4, 5 and 6 identically the same manner of fastening the pads to the collet jaws may be employed as with the push-out collet first described and in 45 fact in Figs. 4, 5 and 6 the method in which the pads of the pull-back collet are seated in the jaws and are detachabl-y fastened thereto is precisely the same aswith the push-out collet first described and, therefore, further description of this part and manner of utilizing my invention need not be described in detail in connection with Figs. 4, 5 and 6 and the corresponding parts of the two constructions are given identical refer- 55 ence characters. Iwish to .point out, however, that the same ease of applying and removal of the pads while the collet is in the machine applies equally well to the collets of the pull-back type as to collets of the push-out type and to .ma- 60 chines which are constructed to accommodate the two types of collets.

' Furthermore inasmuch as I utilize a snap fastener which is preferably located substantially centrally of the pad and substantially centrally 65 of 'the pad receiving surface of the jaw, my invention can be applied with equal advantage to either type of collet, notwithstanding thefact that with the push-out collet the extreme front end of the collet jaws is, due to the tapered surface 3|, relatively thin, as will be seen by Fig. 2, and may be considerably thinner than illustrated in this figure if the collet is designed to accommodate stock of larger diameter than herein illustrated. In other words, with the collet pads dtachably secured to the jaws in accordance 75 with my invention, the latter is equally adapted for all types of collets and with collets whose jaws and pads are adapted to accommodate stock of widely varying sizes and shapes.

With the form of my invention illustrated in Figs. 10 to 13 theconstruction of the collect including the jaws and the pads may be, and preferably is identical with the constructions first described, except for the form of the snap fasteners and the openings which are provided in the jaws and pads to accommodate the fasteners, it being understood that with the construction illustrated in Figs. 10 to 13, each pad is secured to the inner face of the jaw by.a single substantially centrally disposed snap fastener which will now be described. Therefore although the type of fastener illustrated in Figs. 10 to 13. may be utilized with either the push-out or pull-back types of collets, I have shown in Fig. 10 a push-out type of collet 36 with the jaws 31 and the pads 38'formed and shaped as in the similar type of collet illustrated in Figs. 1, 2 and 3. The snap fastener of Figs. 12 and 13 is a tubular member which may be made from heat treated steel. It is provided at one end with a head 39 and a reduced shank which is slotted to form spring fingers 40 with a resilient rounded head ll formed at the free end of the slotted portion or shank. In this instance each jaw has. an

opening 42 iormedtherein to accommodate the head 39 of the fastener, and near its inner end the opening is reduced in size to form a shoulder on which thehead 39 may rest and to permit the passage therethrough of the slotted shank portion III. Formed centrally through the pad is an opening 43 with its end portions oppositely tapered forming an internal shoulder 44 which, in this instance, is somewhat nearer the curved outer face of the pad than the curved inner face.

The shape of the opening 43 and the location of the reduced part or shoulder 44 are such that when the pads are applied the slotted yielding shank 40 of the fastener is inserted into the opening 43 of the pad and when the resilient rounded head II of the fastener passes the internal shoulder 44 at the reduced part of the opening 43 in the pad, it is compressed and then springs outwardly and serves to effectively hold the pad in the jaw while the pad is being in position. Here again by insertion of a suitable tool between the engaging surfaces of the pad and jaw the pad can be separated from and removed from the jaw.

If desired or found necessary the head 39 of the fastener may be given any suitable shape or held in the opening 42 or the jaw in any desired or convenient manner to hold the fastener in place applied or removed. i

It will be understood, of course, that with the type of snap fasteners illustrated in Figs. 10 to 13 the pads can be removed or applied without the necessity of disturbing the collet hood or guard precisely as with the constructions first described.

In machine tools of the type utilizing a stock gripping collet the stock may be fed through the spindle either manually or automatically, and in the latter case a feed collet is employed, which for the sake of simplicity I have not attempted to illustrate in Figs. 1 and 4.

While I have described and illustrated my invention as being applied to a stock gripping collet, it may be employed to advantage in other types of collets as, for example, a feed collet'in machine tools of the general type herein illustrated and referred to in the specification.

While I have shown several forms of my invention I do not desire to be confined to the precise details or arrangements illustrated and.

having spring jaws, and pads on the inner faces 7 of said jaws, means for securing each pad to the associated jaw comprising a resilient snap fastener of the contractible type carried by one member and engaging the other.

2. In a collet comprising a tubular member having spring jaws, and pads on the inner faces of said jaws, means for securing each pad to the associated jaw comprising a snap fastener of the flexing spring finger type carried by one member and engaging the other.

ANTHONY MUSSARI. 

